Pumping systems which are used to pump drilling mud and other abrasive fluids generally incorporate positive displacement pistons or plungers which operate in a reciprocating manner in individual cylinders. Each piston or plunger cylinder has a suction and discharge valve and valve seat operating alternatingly and independently to control flow into and out of each cylinder. The valve typically comprises a disc-shaped body portion which includes an elastomeric valve insert which serves to seal the valve when in the closed position and also serves to cushion the impact of the valve body in the valve seat. A lower conical seating surface of the valve body also makes contact with the valve seat when the valve is in the closed position.
Because of high pump pressures (between 2000 and 5000 psi) and the abrasive solid particles suspended in the drilling mud, valves and valve seats wear at a rapid rate and must be replaced frequently. One of the most significant points of impact stress in the valve assembly is the point of contact of the lower conical portion of the valve body and the valve seat when the valve is in the closed position. The extremely high differential pressures in the valve cause the conical portion of the valve body to engage the valve seat with a very high impact. The repetitive impact eventually causes the faces of the valve body and the valve seat to become worn and pitted. There is a need for an improved valve seat which reduces the impact stress related to the impact of the valve body with the valve seat.
The apparatus of the present invention overcomes the difficulties of the prior art by providing an improved valve seat which significantly decreases the impact stress caused by the impact of a mud pump valve body against the valve seat. The valve seat comprises a generally cylindrical body portion with a sealing surface which is sloped from the outer surface of the cylindrical body portion toward an interior throat of said cylindrical body portion. The valve body comprises a generally disc-shaped portion and a truncated contical portion. An elastomer insert is received in a groove in the valve body. The conical portion of the valve comprises a sloped face, including a metal portion and an elastomeric portion formed by the elastomeric insert. In the valve seat of the present invention, an annular pressure relief groove in the cylindrical body portion of the valve seat allows the sloped face of the valve seat to flex thereby relieving a significant amount of the impact load between the opposing faces of the valve assembly.